Antenna adaptation comparison method for high mobility

ABSTRACT

A system causes a scan angle of a directional antenna to change temporarily from a current scan angle to at least one trial scan angle during reception of predetermined portions of an information carrying signal. At the trial scan angle(s), a trial metric associated with each trial scan angle is determined by the system. The system then selects a next scan angle based on the trial metrics. Examples of predetermined portions of the information carrying signal include the Power Control Bit (PCB) and Forward Error Correction (FEC) block.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. application Ser. No.10/386,364, filed on Mar. 1, 2003 which in turn claims the benefit ofU.S. Provisional Application No. 60/363,669, filed on Mar. 11, 2002 andclaims benefit of U.S. Provisional No. 60/363,214, filed on Mar. 8,2002, which are incorporated by reference as if fully set forth.

BACKGROUND

Code Division Multiple Access (CDMA) communication systems may be usedto provide wireless communications between a base station and one ormore field units. The base station is typically a computer controlledset of transceivers that are interconnected to a land-based publicswitched telephone network (PSTN). The base station includes an antennaapparatus for sending forward link radio frequency signals to the fieldunits. The base station antenna is also responsible for receivingreverse link radio frequency signals transmitted from each field unit.

Each field unit also contains an antenna apparatus for the reception ofthe forward link signals and for transmission of the reverse linkssignals. A typical field unit is a digital cellular telephone handset ora personal computer coupled to a cellular modem. In CDMA cellularsystems, multiple field units may transmit and receive signals on thesame frequency but with different codes, to permit detection of signalson a per unit basis.

The most common type of antenna used to transmit and receive signals ata field unit is a mono-or omni-pole antenna. This type of antennaconsists of a single wire or antenna element that is coupled to atransceiver within the field unit. The transceiver receives reverse linksignals to be transmitted from circuitry within the field unit andmodulates the signals onto the antenna element at a specific frequencyassigned to that field unit. Forward link signals received by theantenna element at a specific frequency are demodulated by thetransceiver and supplied to processing circuitry within the field unit.

The signal transmitted from a monopole antenna is omni-directional innature. That is, the signal is sent with the same signal strength in alldirections in a generally horizontal plane. Reception of a signal with amonopole antenna element is likewise omni-directional. A monopoleantenna does not differentiate in its ability to detect a signal in onedirection versus detection of the same or a different signal coming fromanother direction.

A second type of antenna that may be used by field units is described inU.S. Pat. No. 5,617,102. The system described therein provides adirectional antenna comprising two antenna elements mounted on the outercase of a laptop computer. The system includes a phase shifter attachedto the two elements. The phase shifter may be switched on or off inorder to affect the phase of signals transmitted or received duringcommunications to and from the computer. By switching the phase shifteron, the antenna transmit pattern may be adapted to a predeterminedhemispherical pattern which provides transmit beam pattern areas havinga concentrated signal strength or gain. The dual element antenna directsthe signal into predetermined quadrants or hemispheres to allow forlarge changes in orientation relative to the base station whileminimizing signal loss.

Yet another type of antenna is a scanning directional antenna thatemploys at least one central active antenna element and multiple passiveantenna elements. By changing impedance settings between the passiveantenna elements and a ground plane, a beam produced by the directionalantenna can be scanned in a fixed number of directions related to thenumber of passive antenna elements. An example of such a directionalantenna is described in U.S. Pat. No. 5,767,807 by Pritchett.

SUMMARY

To determine the direction to set the scan angle of a directionalantenna, a controller typically measures the signal-to-noise ratio of asignal, such as a pilot signal, that has a known, constant power outputfrom a base station. The measurement of the pilot signal takes placeduring idle times—times in which there are no data communicationsoccurring between a field unit and base station. Based on themeasurement, a selection of a new scan angle can be made to maximizeantenna gain toward a radio tower associated with the same or differentbase station. An example of such a selection technique is discussed inco-pending U.S. patent application Ser. No. 09/859,001 by Gothard etal., filed May 16, 2001, entitled “Adaptive Antenna for Use in WirelessCommunication System.”

A problem with taking measurements for selecting scan angles during idletimes occurs when the field unit employing a directional antenna is usedin a vehicle traveling at a relatively high rate of speed. In such acase, the “best” scan angle changes while the field unit is “in use,”thereby causing loss of signal strength between the field unit and basestation. The problem may be more noticeable in the case of a field unit,such as a cellular telephone equipped with a directional antenna, beingused by an individual who simply “spins” with the phone, such as at arate of 60 degrees per second. In this case, the gain provided by thedirectional antenna quickly diminishes due to pointing error, and signaldegradation or drop-out may be experienced by the field unit.

To improve performance of field units equipped with directional antennasin a rapidly changing environment, it would be advantageous if a re-scan(i.e., selection of a new scan angle) could occur during non-idle timesand at a high enough rate to minimize signal degradation effects causedby the rapidly changing environment (e.g., the user's spinning).

Accordingly, the principles of the present invention include makingmeasurements to use in the adaptation of a directional antenna. A systememploying the present invention causes a scan angle of the directionalantenna to change temporarily from a current scan angle to at least onetrial scan angle during reception of predetermined portions of aninformation carrying signal. At the trial scan angle(s), a trial metricassociated with each trial scan angle is determined by the system. Thesystem then selects a next scan angle based on the trial metrics.Examples of predetermined portions of the information carrying signalinclude the Power Control Bit (PCB) and Forward Error Correction (FEC)block.

BRIEF DESCRIPTION OF THE DRAWING(S)

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1A is a diagram of a vehicle equipped with a field unit operatingwith a directional antenna according to the principles of the presentinvention;

FIG. 1B is a diagram of an end user with a handset also utilizing theprinciples of the present invention;

FIG. 1C is a diagram of the directional antenna of FIGS. 1A and 1B andassociated antenna beams;

FIG. 2A is a block diagram of a circuit used in the field unit of FIGS.1A or 1B that inserts a Power Control Bit (PCB) into a symbol in anIS-95 wireless communications system;

FIG. 2B is a symbol diagram indicating locations of the Power ControlBit in the symbol produced by the circuit of FIG. 2A;

FIG. 2C is a frame diagram indicating information bits and an FEC blockfor the symbol of FIG. 2B;

FIG. 3 illustrates signal strength and antenna control signals in thefield unit of FIGS. 1A and 1B;

FIG. 4 is a screen shot illustrating simultaneous parameters for thesimulation of FIG. 3;

FIG. 5 is a graph that illustrates how different rotational speeds ofthe field unit of FIGS. 1A and 1B affect convergence;

FIG. 6 is a trace showing why a majority selection algorithm is usefulfor the field units of FIGS. 1A and 1B; and

FIG. 7 is a block diagram of an example circuit that may be employed bythe field unit of FIGS. 1A and 1B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

When referred to hereafter, the terminology “wireless transmit/receiveunit (WTRU)” includes but is not limited to a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of user device capable of operating in a wireless environment. Whenreferred to hereafter, the terminology “base station” includes but isnot limited to a Node-B, a site controller, an access point (AP), or anyother type of interfacing device capable of operating in a wirelessenvironment.

A description of preferred embodiments of the invention follows.

FIG. 1 is a diagram of a wireless communications network 100 in whichthe present invention may be employed. The network 100 may be a CodeDivision Multiple Access (CDMA), Time Division Multiple Access (TDMA),Time Division Duplex (TDD), Frequency Division Duplex (FDD), WiFi,Wireless Local Area Network (WLAN), or other wireless network. Thenetwork 100 includes base stations 105 a, 105 b, 105 c (collectively105) and wireless communications field unit 108 having a directionalantenna 110, such as described in U.S. Pat. No. 6,515,635 by Chiang etal. issued Feb. 4, 2003 or U.S. patent application Ser. No. 09/859,001by Gothard et al., filed May 16, 2001 entitled “Adaptive Antenna for Usein Wireless Communication System,” the entire teachings of both areincorporated herein by reference.

The field unit 108 may be stationary or used in a moving vehicle 115.The field unit 108 may have a current scan angle 120, shown in a solidline, directed to maximize antenna gain for communication with a firstbase station 105 a. The field unit 108 may cause its antenna 112 tochange temporarily from its current scan angle 120 to at least one trialscan angle 125 a, 125 b, 125 c, . . . , 125N. During each of these trialscan angles 125, the field unit 108 determines a metric associated witheach of the trial scan angles 125. Based on the metrics, the field unit108 may cause the scan angle to change from the current scan angle 120to one of the trial scan angles 125 so as to maintain a highsignal-to-noise ratio (SNR) or other metric in a forward or reversepath. This process may be referred to as a re-scan.

Unlike the teachings of the prior art in which re-scan occurs duringidle times (i.e., no data traffic is being communicated between a basestation 105 and the field unit 108), the teachings of the presentinvention allows a re-scan to occur during non-idle times, wherescanning during non-idle times occurs during reception of predeterminedportions of an information carrying signal. Typically, in an IS-95network, for example, the predetermined portion is during a PowerControl Bit (PCB) or Forward Error Correction (FEC) code block, but maybe any time during an information carrying signal that has substantiallylittle effect on the transfer of information in the information carryingsignal. Another such time is during the reception of a CDMA pilotsignal.

A benefit of performing a re-scan during non-idle times is to compensatescan angle during use so as to maintain a high signal-to-noise ratio(SNR), or other signal metric so as to minimize signal loss. Minimizingsignal loss ensures proper data transfer in data transmission or voicequality in voice transmission systems. By re-scanning during non-idletimes, the field unit 108 can rapidly adjust to a rapidly changingenvironment, such as the vehicle's rapid motion on a highway or around acurve, for example.

FIG. 1B is another environment in which a field unit 108, equipped witha directional antenna 110, capable of performing a re-scan duringnon-idle times is useful. In this application, an end user 130 may becommunicating with another person via wireless communications throughthe use of the field unit 108 (e.g., cell phone). The end user 130 maybe quite animated while participating in the conversation. This level ofanimation may manifest itself in rotation, indicated by a pair of arrows135, by the end user 130 during the conversation. The rotation resultsin the current scan angle 120 no longer pointing directly at one of thebase stations 105.

In this case, it is advantageous to have a re-scan process occur duringthe conversion in a manner such that the end user 130 does notexperience a loss of voice quality heard through or transmitted by thefield unit 108. Thus, the current scan angle 120 may be constantlytested by being temporarily changed during reception of predeterminedportions of a voice signal being received or transmitted by the fieldunit 108 to test for a better scan angle, but in a manner such thatthere is substantially no loss of voice quality experienced by the enduser 130. In this case, the current scan angle 120 may be temporarilychanged to a trial scan angle 125 a or 125 b, or both trial scan angles125 a, 125 b may be tested, and one of these trial scan angles 125 a,125 b may be selected to be the next current scan angle. It should beunderstood that if the end user 130 rotates continuously, the currentscan angle 120 may also be changed continuously and, depending on howquickly the end user 130 rotates, the re-scanning process may beemployed very frequently to compensate commensurately.

During the re-scan process, the scan duration of the trial scan angles125 is performed at a rate faster than a data frame, where the dataframe may include a Forward Error Correction (FEC) block. There-scanning process is said to be performed in a “puncturing” mode,where either a known time is predetermined when no data is present, suchas during the Power Control Bit (PCB), or the FEC code is utilized torecover any data lost due to the puncturing through use of the errorcorrection block. Alternatively, the predetermined portion may be lessthan the duration of a single power control command generation period.

The present invention may conditionally utilize a non-data symbol in theblock of a CDMA forward link signal to perform re-scan. In this case, itmay be applied to a W-CDMA, IS-95, or IS-2000 CDMA system, where forwardpower control commands are “punctured” into the data stream to controlthe transmit (TX) power of the reverse link. The conditions under whichit is applied, for example, may be measured on parameters of the RadioFrequency (RF) receive channel.

In the case where the field unit 108 travels at a high velocity (e.g.,in the vehicle 115 of FIG. 1A), the power control of the field unit 108becomes ineffective, since the power control update rate is notsufficient to track the rate at which the environment is changing withrespect to power control. One way to determine the rate at which theenvironment is changing is discussed in co-pending U.S. application Ser.No. 09/772,176, filed Jan. 29, 2001, entitled “Method and Apparatus forDetecting Rapid Changes in a Signaling Path Environment,” the entireteachings of which are incorporated herein by reference. In thoseteachings, for example, one technique for determining rapid changes insignaling environment is through analysis of the variance of the pilotsignal at the output of a baseband demodulator (not shown) inside thefield unit 108.

The predetermined portion, during which trial scan metrics aredetermined, is selected to minimize degradation of the informationcarrying signal. This means that if the information carrying signalincludes voice, the end user 130 should experience substantially nodegradation in voice quality. And, if the information is data, thereshould be substantially no loss of data, optionally measured as afunction of Bit Error Rate (BER).

The predetermined portion of the information carrying signal duringwhich the field unit 108 temporarily changes the scan angle of thedirectional antenna 110 may be during at least one of the following:reception of the Power Control Bit (PCB), low information transfer,receipt of one or more forward error correction (FEC) bits in an FECblock, a time when no time slot has been assigned to the field unit 108,or a time when no payload has been assigned.

The trial metric determined during each trial scan angle 125 may be afunction of at least one of the following: the pilot signal of a forwardlink of a CDMA system, parameters of a control signal, parameters of anassigned payload, or parameters of only forward link signals.

A processor (not shown) in the field unit 108 may determine the trialmetrics. The processor may also determine a current metric associatedwith the current scan angle 120 of the directional antenna 110 andselect a next scan angle that includes comparing a subset of the trialmetrics with the current metric.

Alternatively, the processor may determine multiple trial metrics forthe trial scan angles 125 and select the next scan angle based on themultiple trial metrics. Examples of calculations that may be employedfor handling multiple trial metrics include averaging or accumulatingthe multiple trial metrics. This means that measurements at each trialscan angle 125 are repeated so that the processor may accumulate trialmetrics associated with each of the trial scan angles 125 or may averageeach of these trial metrics. In this multiple measurements case, thefrequency at which the current scan angle 120 is changed to trial scanangles 125 occurs at a high frequency, especially if trying to maintaina high signal-to-noise ratio for a rapidly changing environment, such aswhen the end user 130 rotates with the field unit 108, as depicted inFIG. 1B.

The field unit 108 may utilize information from the forward link todetermine the quality of the current scan angle 120 in a Time DivisionDuplex (TDD) system. In both a TDD system and Frequency Division Duplex(FDD) system, the field unit 108 may transmit a signal at each trialscan angle 125, or subset thereof, and receive a metric from a basestation 105 corresponding to the respective trial scan angles 125. In aTDD system, the field unit 108 may receive metrics from the basestations 105 for selecting a next scan angle in a reverse path or,because TDD systems use the same frequency for forward and reverselinks, the field unit 108 may use metrics from either the forward pathor reverse path to determine a best next scan angle.

In FDD systems, however, the forward link signals and reverse linksignals use different carrier frequencies, so metrics for each path arepreferably determined independently since refraction and multi-pathangles for the forward and reverse paths may differ.

Thus, when used in a TDD system, the field unit 108 may transmit asignal to a base station 105 at each trial scan angle 125 to gleaninformation about the forward and reverse paths. In response to thereverse path transmission, the base station 105 calculates a trialmetric as a function of the received signal. The base station 105 thentransmits the corresponding trial metric to the field unit 108. Thefield unit 108 uses the trial metric to select a next scan angle foreither the forward or reverse path.

The field unit 108 may also determine a received channel parameter, suchas power level, and change a trial scan parameter associated with thetrial scan angles 125 based on the received channel parameter. Forinstance, the trial scan parameter that may be changed may include thescanning rate (i.e., rate at which trial scan angles 125 occur whileattempting to change the current scan angle 120) or adaptation rate(i.e., period or rate at which the current scan angle 120 is attemptedto be improved through selection of a trial scan angle 125). It shouldbe noted that the set of trial scan angles 125 may include the currentscan angle 120 as a trial scan angle 125 during the re-scan process.

The received channel parameters may also include at least one of thefollowing: a signal quality metric, power metric, signal-to-noise ratio(SNR), energy of a chip versus the total interference (Ec/Io), energyper bit versus the total noise (Eb/No), variance in signal power, changein pilot phase, or statistical measure of any one or combination of theabove. Additionally, the received channel parameter may be an automaticgain control (AGC) level crossing rate or variance. Still further, thereceived channel parameter may be based on pilot channel receivedparameters, including at least one of the following: level crossing rateof an envelope of a correlated pilot signal, variance of the envelope ofthe correlated pilot signal, statistical function of the envelope of thecorrelated pilot signal, slew rate of the code phase of the pilotsignal, phase of the pilot signal, variance of the pilot signal, or rateof change of the pilot signal.

The field unit 108 may also detect when direction selection isnon-beneficial. In such a case, the field unit 108 may cause theadaptive antenna 110 to operate in an omni-directional mode. In such acase, for a directional antenna having an active antenna elementsurrounded by a ring of passive antenna elements, each of the passiveantenna elements is set to transmissive mode to form an omni-directionalantenna pattern.

It should be understood that the principles of the present invention arenot limited to a field unit 108 and may be used in base stations 105 or,in a wireless local area network (WLAN), used in an access terminal(AT).

FIG. 1C is an example of the directional antenna 110 that may be usedwith the field unit 108 to provide high gain antenna beam with steeringcapability. The directional antenna 110 includes, in this embodiment,and active antenna element 112 and passive antenna elements 113. Thepassive antenna elements 113 may be used in a transmissive mode orreflective mode. The field unit 108 sets these modes by proper selectionof the coupling, capacitive or inductive, respectively, between thepassive antenna element 113 and ground plane 114. This may be donethrough the use of a simple relay (not shown) that couples either acapacitor or inductor to the passive antenna element 113 and the groundplane 114. Other coupling techniques may also be employed, such as thosetaught in U.S. application Ser. No. 09/859,001 (full citation above).

Continuing to refer to FIG. 1C, in a first configuration, the field unit108 causes the directional antenna 110 to direct the current scan angle120 in a first direction. To generate this scan angle, three passiveantenna elements 113 are set-up as transmissive, as represented by theletter “T” above these passive antenna elements 113, and two of thepassive antenna elements 113 are set-up as reflective, as represented bythe letter “R” above these passive antenna elements 113.

During reception of a first predetermined portion (e.g., Power ControlBit) of an information carrying signal, one of the transmissive passiveantenna elements 113 changes from being transmissive to beingreflective, represented by the “R” above the passive antenna element 113in the second position of the string “T/R/R”. Changing this passiveantenna element 113 to being reflective causes the scan angle to switchfrom the current scan angle 120 to a first trial scan angle 125 a. Atsome later time, during reception of a second predetermined portion ofan information carrying signal, the directional antenna 110 changes thescan angle from the current scan angle 120 to a second trial scan angle125 b. This second scan angle 125 b is generated by having the frontright passive antenna element 113 change from reflective mode totransmissive mode, as indicated by the “T” in the third position in thestring “R/R/T” while the back left passive antenna element 113 remainsin reflective mode, as indicated by the “R” in the third position of thestring “T/R/R”.

FIG. 7 is a block diagram of an example circuit 700 that may be employedby the field unit to perform the re-scan function discussed above. Thecircuit 700 includes a scan controller 705, a processor 710, and aselection unit 715. The scan controller 705 may be coupled to thedirectional antenna 110, either directly or via other circuitry (notshown) to cause a scan angle of the directional antenna 110 to changetemporarily from a current scan angle 120 to at least one trial scanangle 125 during reception of a predetermined portion of an informationcarrying signal. The scan controller 705 may also receive a signal, suchas a communication or pilot signal, from the directional antenna 110.The signal may be an RF, intermediate, or baseband signal that may havebeen processed by other circuitry (not shown) that is capable ofconverting the signal to a form (e.g., digital) capable of beingprocessed by the scan controller 705 and/or processor 710 and selectionunit 715.

The processor 710 is coupled to the scan controller 705 to determine atrial metric associated with each trial scan angle 125. The selectionunit is coupled to the processor to select a next scan angle based onthe trial metrics.

It should be understood that the block diagram is merely an examplearchitecture that may be used to support the re-scan process.Alternative arrangements may be used. For example, the scan controller705, processor 710, and selection unit 715 may be interconnected indifferent ways, implemented in a single processor (e.g., Digital SignalProcessor (DSP)) in software, or hard-wired in a Field Programmable GateArray (FPGA). Additional circuitry (not shown), including memory, logic,and other basic circuit elements may also be included in the circuitry700. Additional signals may also be passed among the circuit components705, 710, 715, and various formats of the signals may be used, such asanalog or digital formats. If implemented in software, the software codemay be stored on digital or optical media and executed by one or moreprocessors to cause the processor(s) to execute the re-scan functionsdiscussed above.

FIG. 2A is a block diagram of a circuit used in an IS-95B communicationssystem to insert Power Control Bits (PCBs) into information frames every1.25 msec (800 Hz). Lower rates are achieved by repeating the FEC blocka number of times; the symbol modulation rate is always 19.2 kHz(approximately 52 microseconds per symbol) giving 24 symbols every 12.5msec, as shown in FIG. 2C.

This circuit is not part of the present invention, but is useful inunderstanding how the PCB is multiplexed into an information signal. Thefield unit 108 knows the location of the PCB and, through use of theprinciples of the present invention, takes advantage of the knowledge ofthe location of the PCB to determine metrics at trial scan angles 125 todetermine whether the current scan angle 120 provides better performancethan the trial scan angles 125.

FIG. 2B is a symbol diagram in the IS-95B standard. Based on the reversetraffic channel in the fifth power control group, a base station 105measures the signal strength of a reverse traffic channel, converts themeasurement to a PCB, and transmits the PCB. In the forward trafficchannel in the seventh power control group, the PCB is transmitted insymbols 11 and 12, as indicated by the long code bits to the left of thezero'th symbol position. In an alternative setting, the PCB may betransmitted in a single symbol. The field unit 108 may take advantage ofthe puncturing times and duration to make trial scan measurements forone or more of the trial scan angles 125. These trial scan measurementsmay use the full duration of the PCB or be less than a single symbolduring which the PCB is transmitted.

The FEC blocks in FIG. 2C are rate ½ encoded and interleaved. These FECblocks may also be “punctured” randomly by inserting the PCBs in placeof the encoded symbols. For example, the 9600 bps frame is encodedgiving 384 encoded symbols every 20 msec, giving 24 symbols every 1.25msec (i.e., 16×24=384). From FIG. 2B, IS-95B “punctures” two symbolsevery 24 symbols to insert the PCB. Since loss of some FEC bits iscorrectable by the FEC algorithm, the FEC block also offers anopportunity to test trial scan angles 125 for improved performance overthe current scan angle 120.

For an adaptive antenna with N predefined antenna patterns, a method ofscanning the array may be as follows. First, a metric of the currentscan angle 120 is measured. Next, the scan angle is re-pointed and asecond measurement (i.e., trial scan angle 125) is made. The twopositions are then compared and the better is selected. The comparisonmay be based on one set of measurements or M sets prior to the decisionto retain or re-point the directional antenna 110 is made. Next, theselected scan angle is re-measured and compared with another new scanangle of the M total scan angles. The differential measurements may bemade continuously, optionally incrementally comparing all trial scanangles 125 with a best current scan angle 120.

This may be done for a 3-position antenna as shown in Table 1. TABLE 1Current Time period Scan Angle Trial Scan Angle Next Scan Angle A -Change Omni Left Left B - No Change Left Right Left C - No Change LeftOmni Left D - No Change Left Right Right E - Change Right Omni Right F -No Change Right Left Right

This may additionally be performed for the transmitter from the fieldunit 108 utilizing the directional antenna to transmit. In this case,feedback from the Base Transceiver Station (BTS) over the forward linkis required when used in a Frequency Division Duplex (FDD) mode. ForTime Division Duplex (TDD) systems, no feedback is required, but may beused.

Discussed below is a simulation program that allows exploration of therelationships between puncturing frequency (i.e., the cycles stolen fromthe normal power control to make measurements on a new directionalantenna scan angle), the speed of the field unit 108, the optimal numberof samples required to make a steering decision, and the degrees persecond at which the field unit 108 is allowed to rotate withoutsuffering significant signal degradation.

FIG. 3 is a chart of signal strength 305 (Jakes model on the top graph)fluctuating for a user moving at 3 miles per hour. The chart represents2 seconds of time.

The lower mostly horizontal lines 310 a, 310 b, 310 c, 310 d eachrepresent one of the ten antenna positions (reading on the right handscale). The directional antenna 110 compensates a rotation of the fieldunit 108 of 60 degrees per second in this example.

The curve 315 in the middle represents the power-corrected signal. Every16 milliseconds (the puncturing cycle), it is possible to see that thedirectional antenna 110 was rotated to a sub-optimal position, and,consequently, the signal level dropped. This had no effect on the datastream since the position was not selected.

The above simulation also shows a curve 320 (in black at the bottom),which represents +/−power normal control bits (at 800 Hz). The blackvertical lines 325 in this curve 320 indicate control bits received inerror.

The scanner shot of FIG. 4 shows some of the parameters and thepossibilities of the simulation program.

As an example, a user may select a Cumulative Distribution Function ofthe (SNR-TARGET_SNR) with a variety of rotational speeds for the fieldunit 108. Other exemplary selectable parameters in the GUI window foroperating the simulation are also shown.

The curves of FIG. 5 represent rotations of 0 (top curve), 30 (second),60 (third) and 90 (bottom curve) degrees per second, respectively, forthe field unit 108, such as in the rapidly changing signalingenvironment of FIG. 1B. Referring to FIG. 5, if the field unit 108rotates at 0 degs/dec, 1% of its sample metrics are at −3 dB. Bycomparison, for a rotation of 60 degs/sec, 1% of its samples are −4 dB;and for a rotation of 90 degs/sec, 1% of its samples are −9 dB.

FIG. 6 is a trace showing why a majority-selection algorithm or othersuitable algorithm may be useful for antenna scan selection. Because ofmany errors in power assessments, the antenna scan angle may be updatedfrequently to compensate for a rapidly changing environment.

In the trace, while the directional antenna 110 is set to current scanangle 120 number “3”, trial scan angles 125 are tested for signalstrength comparison. As indicated, the following trial scan angles 125were found to be better than scan angle #3: “3 5 3 2 2 3 2 1”. Based onthese results, scan angle #2 is selected as the next scan angle since itwas selected three out of eight times as the best scan angle accordingto a given metric, such as SNR. The next trace results in the scan anglebeing changed to scan angle #1 for similar reasons.

The rate and period of the re-scan may be changed based on thedetermined link stability or velocity. For instance, at moderate speeds,the scan may be performed once every other frame or 1/32 commands. Forhigh velocity, it may be performed continuously. The velocity of thevehicle 115 (FIG. 1) may be determined as described in U.S. patentapplication Ser. No. 09/772,176 (full citation above). Examples of thisinclude Automatic Gain Control (AGC) variation, Doppler, and levelcrossing rate of the correlated pilot signal.

In using the Level Crossing Rate of AGC signal to measure mobilevelocity, the AGC output signal may be corrupted by Additive WhiteGaussian Noise (AWGN). Therefore, the AGC Level Crossing Rate does notrepresent Rayleigh fading fluctuation well. Instead of AGC LevelCrossing Rate, a more preferable method may be to use the Level CrossingRate of Pilot signal envelope (√{square root over (I²+Q²)}) which comesfrom an Access Terminal baseband demodulator (not shown). The Pilotsignal envelope represents the Rayleigh fading variation well and it isless affected by AWGN.

If variance is the measured metric instead of AGC, the continuousforward link Pilot signal variance is more proportional to the fadingvariation.

Further, there may be conditions when these parameters indicate that nodirectional position is likely to be beneficial and scanning may behalted. In this case, the directional antenna 110 may be steeredomni-directional.

Additionally, when the power control is effective at slow or mediumvelocities or channel variations, it may be useful to scan thedirectional antenna 110 at a rate that is faster than the forward powercontrol loop can respond to adjust the TX power significantly. Scanningat a rate that is relatively slow may cause excess jitter in the forwardpower control loop as the commands response to the scanning processrather than the channel.

The principles of the present invention additionally includes theconcept of scanning at a rate that minimize the impact to the forwardcontrol loop. For instance, in practice, a Power Control Bit (PCB) isgenerated based on a measurement duration of 1.25 ms. The PCB istransmitted at this period as well, but over a significantly shorterperiod of time (e.g., 1 symbol or 64 chips). Each PCB typically adjuststhe power by 1 dB. If the scan is N*1.25 ms periods long (power controlgroups), a trial scan angle 125 has the potential of modifying theforward power significantly. If the trial scan angle 125 is limited toone or less power control group (PCG), the impact of a bad position inminimized. Further, if the re-scan trial scan angle 125 is a fraction ofthe PCG period, the impact to the command error is further minimized.Since the PCB itself is only a fraction of the PCG, scanning during thePCB time lessens any forward power control impact from the scanningprocess.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

Although the features and elements of the present invention aredescribed in the preferred embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the preferred embodiments or in various combinations with orwithout other features and elements of the present invention. Themethods or flow charts provided in the present invention may beimplemented in a computer program, software, or firmware tangiblyembodied in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) module.

1. A method for adapting a directional antenna by a wirelesstransmit/receive unit (WRTU) during a non-idle time comprising: causinga scan angle of the antenna to change temporarily from a current scanangle to at least one trial scan angle during the reception of aninformation carrying signal; determining a metric associated with eachof the trial scan angles; and selecting a next scan angle based on thetrial metrics.
 2. The method of claim 1, wherein said changing of thescan angle is conducted during reception of a Power Control Bit (PCB) tominimize the effect on the transfer of information in the informationcarrying signal.
 3. The method of claim 1, wherein said changing of thescan angle is conducted during reception of a forward error correction(FEC) code block to minimize the effect on the transfer of informationin the information carrying signal.
 4. The method of claim 1, whereinsaid changing of the scan angle is conducted during reception of a pilotsignal to minimize the effect on the transfer of information in theinformation carrying signal.
 5. The method according to claim 2, whereinthe dwell time of the Power Control Bit is less than the duration of asingle power control command generation period.
 6. The method accordingto claim 2, wherein the Power Control Bit (PCB) is during at least oneof the following: low information transfer; receipt of one or moreForward Error Correction (FEC) bits in an FEC block; a time when notraffic channel is assigned; or a time when no payload is assigned. 7.The method according to claim 1, wherein the trial metrics are afunction of at least one of the following: parameters of a controlchannel; parameters of an assigned traffic channel; or parameters of anyforward link channel.
 8. The method according to claim 1, furtherincluding: determining a current metric associated with a current scanangle of the antenna; and selecting a next scan angle includes comparinga subset of trial metrics with the current metric.
 9. The methodaccording to claim 1, further including: determining multiple trialmetrics for the trial scan angles; and selecting a next scan angle takesthe multiple trial metrics into account.
 10. The method according toclaim 7, further including averaging or accumulating the multiple trialmetrics.
 11. The method according to claim 1, further includingutilizing information from the forward link to determine the quality ofthe current scan angle for Time Division Duplex (TDD) systems.
 12. Themethod according to claim 1, further including: transmitting a signal ateach trial scan angle and receiving a metric corresponding thereto froma base station; and using the received metrics for selecting a next scanangle in a reverse path.
 13. The method according to claim 12, used in aFrequency Division Duplex (FDD) or Time Division Duplex (TDD) system.14. The method according to claim 1, used in a TDD system, wherein ateach trial scan angle, the method further includes: transmitting asignal to a base station; and wherein determining a trial metricincludes receiving the trial metric from the base station.
 15. Themethod according to claim 1, further including determining a receivedchannel parameter and changing a trial scan parameter based on thereceived channel parameter.
 16. A wireless transmit/receive unit (WRTU)in a wireless communication system for communicating with a basestation, wherein said WRTU adapts a directional antenna during anon-idle time comprising: a scanned controller to cause a scan angle ofthe antenna to change temporarily from a current scan angle to at leastone trial scan angle during the reception of an information carryingsignal; a processor coupled to the scanned controller to determine ametric associated with each of the trial scanned angles; and a selectionunit coupled to the processor to select a next scan angle based on thetrial metrics.
 17. The WRTU of claim 16, wherein the scan angle ischanged during reception of a Power Control Bit (PCB) to minimize theeffect on the transfer of information in the information carryingsignal.
 18. The method of claim 16, wherein said scan angle is changedduring reception of a Forward Error Correction (FEC) code block tominimize the effect on the transfer of information in the informationcarrying signal.
 19. The method of claim 16, wherein the scan angle ischanged during reception of a pilot signal to minimize the effect on thetransfer of information in the information carrying signal.
 20. The WRTUaccording to claim 16, wherein the dwell time of the Power Control Bit(PCB) is less than the duration of a single power control commandgeneration period.
 21. The WRTU according to claim 16, wherein the PowerControl Bit (PCB) is during at least one of the following: lowinformation transfer; receipt of one or more Forward Error Correction(FEC) bits in an FEC block; a time when no traffic channel is assigned;or a time when no payload is assigned.
 22. The WRTU according to claim16, wherein the metrics are a function of at least one of the following:parameters of a control channel; parameters of an assigned trafficchannel; or parameters of any forward link channel.
 23. The WRTUaccording to claim 16, wherein the processor determines a current metricassociated with a current scan angle of the directional antenna and theselection unit selects a next scan angle by comparing a subset of trialmetrics with the current metric.
 24. The WRTU according to claim 16,wherein the processor determines multiple trial metrics for the trialscan angles and the selection unit selects a next scan angle by takingthe multiple trial metrics into account.
 25. The WRTU according to claim24, wherein the processor includes an arithmetic unit to average oraccumulate the multiple trial metrics.
 26. The WRTU according to claim16, wherein the processor uses the selected scan angle to determine thequality of the scan angle for Time Division Duplex (TDD) systems. 27.The WRTU according to claim 16, further including: a transceiver totransmit a signal at each trial angle and receive a metric correspondingthereto from a base station; and wherein the processor coupled to thetransceiver uses the received metrics for selecting a next scan angle ina reverse path.
 28. A WRTU according to claim 16, used in a FrequencyDivision Duplex (FDD) or Time Division Duplex (TDD) system.
 29. The WRTUaccording to claim 16, used in a TDD system, wherein at each trial scanangle, the processor transmits a signal to a base station andresponsively receives the trial metric from the base station.
 30. TheWRTU according to claim 16, wherein the processor receives a channelparameter and changes a trial scan parameter based on the receiverchannel parameter.